INSTALLATION OF TIE-IN POINTS
From F- 1 dust flter
SENSITIVITY OF INCREASING RECYCLE FLOW AS REFLUX
Residue-gas recycle fow rate as refux
5 MMscfd 6 MMscfd 7 MMscfd
74 76 79
98 99 99
2,660 2,665 2,665
280 330 390
Ethane recovery, %
Propane recovery, %
densed, subcooled, and sent as reflux to the demethanizer.
This additional methane-rich reflux from residue-gas recycle provides enhanced rectification of tower vapor so that
more ethane and heavier components can be recovered.
The design redeploys one of the prechilling branches for
the inlet gas to cool the residue gas and further chill it in a
This option would require additional compressor and
gas/gas heat exchanger. Pioneer preferred to reuse an idled
compressor, KR- 104. Previously, 10 MMscfd of residue gas
was compressed by this compressor and sent as sales gas.
Fig. 3 illustrates the addition of residue-gas recycle to demethanizer as reflux. The new route appears as the dashed
Table 1 shows the sensitivity of increasing residue-gas recycle as reflux on the process performance.
With 8. 6 MMscfd recycle rate, the
ethane and propane recoveries improve to 85% and 99%, respectively.
The propane refrigeration load also
increased but was within the equipment’s capacity.
Two existing idled brazed aluminum heat exchangers (BAHX), EP-313
and EP-314, were identified as candidates for the residue-gas chiller. Eventually EP-313 was determined more appropriate because of
the similarity between its original design and the new service. The exchanger was then rerated to confirm its suitabil-ity.
Table 2 summarizes the ethane recovery increase and associated equipment and operational changes for each retrofit
option. Clearly, Option 6 had the largest ethane recovery
As can be seen, several other options were also identified
for potential ethane recovery increase. Pioneer will be able
to use this insight to plan further operational improvements.
8 MMscfd 8. 6 MMscfd
Pioneer chose to Option 6 and decided to purchase new
compressors to produce 15 MMscfd of reflux to achieve even
higher ethane recovery. The longer lead times for new compressors, however, made it appealing to use the existing resi-